Numerous medical devices require fine motor skills to effectively and safely provide some form of treatment. A common example would be a medical provider performing a procedure in which a medical instrument is placed into a precise location in the body under imaging guidance. While experience aids medical providers in knowing the appropriate location and manipulations needed to perform the procedure, mechanisms to aid the placement of a device results in greater accuracy, consistency, patient safety, patient comfort, reduced radiation exposure, and shorter duration with regard to procedures.
The majority of computed tomographic (CT) guided procedures involve placing a medical instrument into a target lesion. Example procedures include injections, biopsies, ablations, catheter placement, and fiducial placements. In performing these procedures, in most instances a CT scan is initially performed which allows the operator to evaluate the target of the medical device, and plan a course from the entry point of the device into the patient. Once the target and entry point are determined and, after making sure the course does not transgress a critical structure, the angle of approach can be determined with respect to the orientation of the CT scanner by software and displayed on the CT images on the displays used to control the scanner.
Once the trajectory determined by the target and entry point, and the angle of that line in respect to the CT scanner have been determined, the operator advances the medical device along that course, intermittently rescanning the area to determine the actual position of the medical device and its relation to the intended course, and adjusting as necessary. CT scanners will usually have a laser line that projects from the scanner in the transaxial plane onto the patient to aid in localizing the entry point. However, re-scanning during the procedure is necessary to ensure proper positioning of the device, and any alterations from the planned course require re-positioning of the device and thus result in additional movement of the medical device along, or outside of the pre-determined path. This additional movement, and rescanning to ensure proper positioning of the device increases radiation exposure to the patient, prolongs procedure time, can cause additional trauma to organs within or near the intended trajectory, and may increase pain experienced by the patient.
Many medical device guidance systems have been developed to aid in positioning and movement of the medical instrument. A major limitation with some of these medical device guidance systems is that such systems constrain the motion of the medical device with respect to a patient, bench, CT scanner, room, or some other fixed reference. For example, US 20130066232 discloses a device for trajectory guidance of a needle-like medical instrument through the use of an accelerometer and a line generating laser which is aligned with the laser line of the CT scanner. A needle-like medical instrument is inserted through a rotatable guide sleeve which is locked into a desired orientation based on an initial diagnostic and planning CT scan. The guide sleeve is attached to a base which is constrained with respect to the room or CT scanner. The guide sleeve constrains the trajectory of the needle like medical instrument after the desired orientation is determined. Simple intra-procedural adjustments to the trajectory of the needle-like instrument which can be a common occurrence due to patient motion or when targeting organs subject to respiratory motion, for example, may be extremely cumbersome with this device. In addition, once a needle-like medical instrument is inserted into a patient and is constrained in this manner, any type of patient motion, for example something as common as a cough, may cause significant organ injury such as a major laceration of the organ in which the instrument has been inserted.
Other devices determine orientation by using some combination of accelerometers, gyrometers, magnetometers, optical cameras, GPS, and radiofrequency signaling all with some limitations. For example, US Publication No.'s 20140135616, 20140107471, 20140180074, 20130064427, 20140088410, U.S. Pat. No. 6,611,141, and DE4225112 all disclose devices for medical instrument guidance using some combination of the aforementioned technologies. Accelerometers only measure orientation with respect to gravity limiting their ability to determine 3-dimensional orientation independently. Accuracy of magnetometers is limited in the presence of electromagnetic interference such as from a CT scanner. Gyrometers are prone to rapid signal drift requiring reorientation from a magnetometer or an external reference. Optical cameras determine position of the medical devices relative to fixed references or markers which constrain the device to be within the field of view of the camera and require additional hardware and software. GPS and radiofrequency signaling also require additional hardware and software for sending, receiving, and processing the signals.
In comparison to the prior art devices, the present device provides an effective, simple to use, fast, and inexpensive means of determining 3-dimensional orientation of a medical instrument for the purpose of guidance during a medical procedure. The present device combines a CT scan with a secondary laser and guidance system that allows completely unconstrained movement of a medical instrument, contains all of the required hardware and software in a compact lightweight design, and is compatible with nearly all needle-like medical instruments commonly used during CT-guided procedures.